This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Double-quantum coherence ESR spectroscopy was created and developed at ACERT into a state-of-the-art technique;however it was eventually implemented by Bruker in commercial spectrometers and is available to the research labs that have purchased them. In our hands this technique provides a wider distance range and in many important cases superior sensitivity compared to commonly-used DEER. The sensitivity of DQC at Ku band at ACERT exceeds the sensitivity of DEER in commercial spectrometers by more than an order of magnitude. In part this is due to the uniqueness of ACERT PDS spectrometers, but even with commercial spectrometers operating at X-band one can benefit from using this technique. Also, the technique was implemented at ACERT in 2D format, which provides information on orientations in a single experiment. However, using DQC does require a certain level of expertise, which ACERT will readily provide to the interested parties. Recently, a Postdoctoral associate of Wayne Hubbell, Dr. Yang, Zhongyu, has visited ACERT for several days, where he was participating in conducting DQC spectroscopy on his sample that had ESR spectrum far too narrow for DEER. All aspects of tuning and running DQC pulse sequence have been successfully demonstrated on his samples and Dr. Freed provided several important insights into the technique to the trainee. We hope that this training session would help stimulate a routine use of DQC in Hubbell's lab.